The Address Resolution Protocol (ARP) is used to map IP addresses to MAC addresses in a local network.
ARP operates at the data link layer (Layer 2) of the OSI model and is essential for communication within a LAN.
* ARP Request :
* When a device needs to communicate with another device on the same network but does not know the destination's MAC address, it sends an ARP Request .
* Since the sender does not know the MAC address of the destination, it cannot send the request directly to the destination using unicast. Instead, the ARP Request is sent as a broadcast packet to all devices on the local network.
* The broadcast packet has a destination MAC address of FF:FF:FF:FF:FF:FF, which ensures that all devices on the network receive the packet.
* ARP Response :
* The device with the matching IP address responds with an ARP Reply , which is sent as a unicast packet back to the requesting device.
* Why Not Other Options?
* Anycast : This involves sending packets to the nearest device in a group of devices sharing the same IP address. ARP does not use anycast.
* Unicast : ARP Requests cannot be sent as unicast because the sender does not yet know the destination's MAC address.
* Multicast : Multicast is used for sending packets to a specific group of devices, but ARP Requests are sent to all devices on the network, making broadcast the correct choice.
Thus, ARP Requests are transmitted as broadcast packets .
References:
* HCIA Huawei ACCESS Official Documentation , Chapter: ARP Protocol and Operation.
* Ethernet Networking Fundamentals by Huawei.